I'll add another non-technical reason: ML is a Google core-competency, and has been for some time now[1], but it is/was not central to Apple. 1. Google 411 was

I'll add another non-technical reason: ML is a Google core-competency, and has been for some time now[1], but it is/was not central to Apple. 1. Google 411 was introduced 13 years ago, in 2007, and look at the ML papers published and techniques Google pioneered since then.